Method and system for dating blood pools

Abstract

A computer-implemented method and a system for dating a blood pool lying on a substrate are described. The method comprises: determining, based on at least one picture of a blood pool lying on a substrate taken at a given time (t), the drying front of the blood pool at the given time (t); and determining, based on the determined drying front of the blood pool at the given time (t), and on a drying model, the time elapsed between the given time (t) and an initial time (t0) at which the blood pool initiated a drying process on the substrate. Determining the drying front of the blood pool comprises determining the wet perimeter (Pt) of the blood pool, and the drying model correlates the time elapsed with a blood's diffusion coefficient (Dblood) measured for a plurality of predetermined environmental conditions and a plurality of initial blood pool conditions.

1 . Computer-implemented method for dating a blood pool lying on a substrate, comprising:
 determining, based on at least one picture of a blood pool lying on a substrate taken at a given time, the drying front of the blood pool at the given time,   determining, based on the determined drying front of the blood pool at the given time, and on a drying model, the time elapsed between the given time and an initial time at which the blood pool initiated a drying process on the substrate,   wherein determining the drying front of the blood pool at the given time comprises determining the wet perimeter of the blood pool at the given time, and   wherein the drying model correlates the time elapsed with a blood's diffusion coefficient measured for a plurality of predetermined environmental conditions and a plurality of initial blood pool conditions.   
     
     
         2 . The computer-implemented method of  claim 1 , wherein the drying model correlates the time elapsed with a blood's diffusion coefficient by means of blood pool parameters including the blood pool's height. 
     
     
         3 . The computer-implemented method of  claim 1 , wherein the time elapsed between the given time and the initial time is determined by:
 providing a database comprising sets of predetermined environmental and initial blood pool conditions including initial areas, the sets of predetermined environmental and initial blood pool conditions being associated with corresponding sets of measured blood pool parameters including blood's diffusion coefficients and blood pool's heights,   determining the environmental conditions to which the blood pool is exposed at the given time, and an initial area of the blood pool corresponding to the area of the blood pool at the initial time,   comparing the determined environmental conditions and the determined initial area with the sets of predetermined environmental and initial blood pool conditions, and   determining a set of measured blood pool parameters comprising the blood's diffusion coefficient and the blood pool's height associated with the set of predetermined environmental and initial blood pool conditions matching with the determined environmental conditions and the determined initial area.   
     
     
         4 . The computer-implemented method of  claim 1 , wherein the predetermined environmental conditions comprise at least the temperature and humidity of the environment to which the blood pool is exposed, and the nature of the substrate on which the blood pool lies. 
     
     
         5 . The computer-implemented method of  claim 1 , wherein the drying model comprises a function correlating the time elapsed between the given time and the initial time with the blood's diffusion coefficient, the blood's diffusion coefficient having a substantially constant value during the time elapsed between the given time and the initial time for the same environmental conditions,
 wherein the blood's diffusion coefficient is expressed according to the following equation:
     D   blood   =K   i   L   k   L*   0.5   (1)
 
   wherein:
 D blood  is the blood's diffusion coefficient; 
 K i  is a coefficient of transfer from the liquid state into the gaseous state and is expressed according to the following equation: 
   
       
         
           
             
               
                 
                   
                     
                       K 
                       i 
                     
                     = 
                     
                       
                         J 
                         * 
                       
                       ⁢ 
                       
                         
                           R 
                           ⁢ 
                           T 
                         
                         
                           M 
                           ⁢ 
                           
                             P 
                             w 
                           
                         
                       
                     
                   
                 
                 
                   
                     ( 
                     2 
                     ) 
                   
                 
               
             
           
         
         wherein:
 M is the molecular weight of water; 
 P w  is the saturation vapor pressure of water at the surface of the blood pool; 
 R is the ideal gas constant; 
 T is the temperature of the environment to which the blood pool is exposed; and 
 J* is the evaporation rate of the blood pool and is expressed according to the following equation: 
 
       
       
         
           
             
               
                 
                   
                     
                       J 
                       * 
                     
                     = 
                     
                       
                         
                           δ 
                           ⁢ 
                           m 
                         
                         
                           δ 
                           ⁢ 
                           t 
                         
                       
                       × 
                       
                         1 
                         
                           A 
                           0 
                         
                       
                     
                   
                 
                 
                   
                     ( 
                     3 
                     ) 
                   
                 
               
             
           
         
         wherein:
 δm/δt is the mass variation of the blood pool with time; and 
 A 0  is the area of the blood pool at the initial time (t 0 ); 
 
         L k  is the Knudsen layer and is expressed according to the following equation: 
       
       
         
           
             
               
                 
                   
                     
                       L 
                       k 
                     
                     = 
                     
                       
                         
                           k 
                           B 
                         
                         ⁢ 
                         T 
                       
                       
                         π 
                         ⁢ 
                         
                           d 
                           2 
                         
                         ⁢ 
                         
                           P 
                           a 
                         
                       
                     
                   
                 
                 
                   
                     ( 
                     4 
                     ) 
                   
                 
               
             
           
         
         wherein:
 k B  is Boltzmann's constant; 
 d is the molecular diameter of water molecules; and 
 P a  is the atmospheric pressure; 
 
         L* is a shape factor and is expressed according to the following equation: 
       
       
         
           
             
               
                 
                   
                     
                       L 
                       * 
                     
                     = 
                     
                       
                         A 
                         0 
                       
                       
                         
                           P 
                           t 
                         
                         ⁢ 
                         h 
                       
                     
                   
                 
                 
                   
                     ( 
                     5 
                     ) 
                   
                 
               
             
           
         
         wherein:
 h is the blood pool's height; and 
 P t  is the wet perimeter. 
 
       
     
     
         6 . The computer-implemented method of  claim 1 , wherein determining the drying front of the blood pool at the given time further comprises determining the wet area of the blood pool at the given time. 
     
     
         7 . The computer-implemented method of  claim 1 , wherein the drying model comprises a function correlating the mass variation of the blood pool with time with the wet area of the blood pool at the given time. 
     
     
         8 . The computer-implemented method of  claim 7 , wherein the function correlating the mass variation of the blood pool with time with the wet area of the blood pool at the given time is expressed according to the following equation: 
       
         
           
             
               
                 
                   
                     
                       
                         δ 
                         ⁢ 
                         m 
                       
                       
                         δ 
                         ⁢ 
                         t 
                       
                     
                     = 
                     
                       - 
                       
                         
                           α 
                           ⁢ 
                           
                             
                               
                                 m 
                                 0 
                               
                               [ 
                               
                                 1 
                                 - 
                                 
                                   ( 
                                   
                                     
                                       A 
                                       t 
                                     
                                     
                                       A 
                                       0 
                                     
                                   
                                   ) 
                                 
                               
                               ] 
                             
                             β 
                           
                         
                         
                           δ 
                           ⁢ 
                           t 
                         
                       
                     
                   
                 
                 
                   
                     ( 
                     6 
                     ) 
                   
                 
               
             
           
         
         wherein:
 α and β are correlation coefficients constant at the environmental conditions to which the blood pool is exposed at the given time (t); 
 A t  is the wet area of the blood pool at the given time (t); 
 δt is the time elapsed between the given time (t) and the initial time (t 0 ); 
 δm is the mass variation of the blood pool during the time elapsed between the given time (t) and the initial time (t 0 ); 
 m 0  is the mass of the blood pool at the initial time (t 0 ) and is expressed as according to the following equation:
     m   0   =A   0   ρh   (7)
 
 
 
         wherein:
 ρ is the blood's volume weight. 
 
       
     
     
         9 . The computer-implemented method of  claim 8 , wherein the time elapsed between the given time and the initial time is expressed according to the following equation: 
       
         
           
             
               
                 
                   
                     
                       δ 
                       ⁢ 
                       t 
                     
                     = 
                     
                       
                         α 
                         ⁢ 
                            
                         
                           Rk 
                           B 
                         
                         ⁢ 
                         
                           T 
                           2 
                         
                         ⁢ 
                         
                           A 
                           0 
                           
                             1 
                             / 
                             2 
                           
                         
                         ⁢ 
                         
                           h 
                           
                             1 
                             / 
                             2 
                           
                         
                         ⁢ 
                         
                           
                             ρ 
                                
                             [ 
                             
                               1 
                               - 
                               
                                 ( 
                                 
                                   
                                     A 
                                     t 
                                   
                                   
                                     A 
                                     0 
                                   
                                 
                                 ) 
                               
                             
                             ] 
                           
                           β 
                         
                       
                       
                         π 
                         ⁢ 
                         
                           d 
                           2 
                         
                         ⁢ 
                         M 
                         ⁢ 
                         
                           P 
                           t 
                           
                             1 
                             / 
                             2 
                           
                         
                         ⁢ 
                         
                           D 
                           blood 
                         
                         ⁢ 
                         
                           P 
                           w 
                         
                         ⁢ 
                         
                           P 
                           a 
                         
                       
                     
                   
                 
                 
                   
                     ( 
                     8 
                     ) 
                   
                 
               
             
           
         
       
     
     
         10 . The computer-implemented method according to  claim 8 , wherein the sets of measured blood parameters further comprise the correlation coefficients α and β. 
     
     
         11 . The computer-implemented method according to  claim 1 , comprising the repetition of at least the steps of  claim 1  a predetermined number of times. 
     
     
         12 . System for dating a blood pool lying on a substrate, comprising:
 means for determining, based on at least one picture of a blood pool lying on a substrate taken at a given time, the drying front of the blood pool at the given time; and   means for determining, based on a drying model and on the determined drying front of the blood pool at the given time the time elapsed between the given time and an initial time at which the blood pool initiated a drying process on the substrate,   wherein the means for determining the drying front of the blood pool at the given time determines the wet perimeter of the blood pool at the given time, and   wherein the means for determining the time elapsed between the given time and the initial time correlates the time elapsed with a blood's diffusion coefficient measured for a plurality of predetermined environmental conditions and a plurality of initial blood pool conditions.   
     
     
         13 . System according to  claim 12 , wherein:
 the means for determining the drying front of the blood pool at the given time comprises an image processing software;   the means for determining the time elapsed between the given time and the initial time comprises a calculation software; and   wherein the system further includes a database comprising sets of predetermined environmental and initial blood pool conditions including initial areas, the sets of predetermined environmental and initial blood pool conditions being associated with corresponding sets of measured blood pool parameters including blood's diffusion coefficients and blood pool's heights.